1. Field of the Invention
The present invention relates to a method and a device for the measurement of wind-related stresses on a rotating system, notably for a radar with rotating antennas.
A particular field of application of the invention relates to radars set up on the ground and used to detect moving targets of all types, said radars comprising a system of rotating antennas without protection against the effects of the wind. For such radars, the effects of the wind have two main consequences:
The forces due to the wind, to which the system is subjected, are such that it is desirable to stop the rotational driving of the antennas beyond a certain wind velocity, typically between 120 and 130 km/h, in so as to prevent any risk of deterioration and premature wearing out of the rotary plate that supports the antennas and the motor drive system;
Even below this wind velocity limit, there is a deformation, or torsion, of the system of antennas that modifies their radiation characteristics and leads to an error in the measurement of the azimuthal angle of the detected targets.
2. Description of the Prior Art
A known way of permanently measuring the velocity of the wind uses anemometrical sensors which trigger the stopping of the drive motors of the rotary plate and their uncoupling as soon as the prescribed limit is reached, so that the system of antennas can take its orientation freely as dictated by the wind. However, the measurement made by these sensors is generally distorted by the proximity of the antennas. Furthermore, the adding on of these sensors, which are positioned externally and are quite naturally connected to the electronic circuitry of the radar, significantly increases the risk of the propagation of lightning into this electronic circuitry.
With respect to the strain related to the deformation of the system of antennas, specialists have had either to shield the system by means of radomes that are permeable to the radar waves and are rain-proof and wind-proof, or to strengthen the mechanical structures of the antennas. However, neither of these two approaches is entirely satisfactory, the former because the radome necessarily contributes disturbance to the radiation of the antennas and the latter because it is incompatible with the imperatives of weight and cost.